The invention relates to a method for continuous coating of substrates, in which the substrates are transported continuously through a deposition chamber and, at the same time, measures are adopted for reducing parasitic deposits as well as possible. Likewise, the invention relates to a corresponding device for continuous coating of substrates.
It is still an essential aspect for the design of coating plants to produce continuous educt and product flows. However, in the case of coating plants for continuous coating which are known from the state of the art, undesired concomitant phenomena occur during the deposition process.
There are included herein:                The geometry of the deposition chamber can be changed and hence the gas flows. In the case of some deposition conditions, this has an effect on the layer homogeneity and the layer quality.        Transport paths can be blocked by parasitic layers or particles, or friction can be increased, which can lead to blockage of a carrier transport.        Gas paths can be blocked, which can lead to gas escape and hence possibly dangerous situations.        Parasitic layers can flake off, which leads to particle formation in the deposition chamber and hence to “poor” layers, possibly even to total economic loss of the layer.        The uptime of the plant is made worse because the deposits often can be etched back.        
To date, different solution concepts have been proposed for the problems listed here (S. Reber et al., CONCVD and PROCONCVD: Development of High-Throughput CVD Tools on the Way to Low-Cost Silicon Epitaxy, 24th European PV Solar Energy Conference and Exhibition, Hamburg and A. Hurrie et al., High-Throughput Continuous CVD Reactor for Silicon Deposition, 19th European Photovoltaic Solar Energy Conference, 2004).
Included herein is the regular cleaning by means of in-situ etching-back of the parasitic layers. However, this method cannot be applied with some layers, e.g. silicon carbide, since these layers are etch-resistant.
Another approach for eliminating parasitic deposits is based on regular ex-situ cleaning. However, this is associated with additional time expenditure.
Furthermore, parasitic deposits can be removed by regular exchanging of the parasitically coated surfaces being effected. However, this represents an expensive variant.
Another approach is based on “high-quality” surfaces being protected from parasitic deposits by means of a cover material. This cover material can be either cleaned ex-situ or exchanged.
Furthermore, it is known to solve the mentioned problems by avoiding contact of the surfaces with process gas by directed gas flow, e.g. gas curtains, gas cushions, etc. However, this variant can only prevent the production of parasitic deposits in a limited manner.